Control system



Nov. '26, 1940;

T. R. HARRISON CONTROL SYSTEM Original Filed Jan. 9, 1957 2 Sheets-Sheet1 FIG. I.

WV INVENTOR T THOMAS RHARRISON I BYQ ,1P 6),... Q

. ATTORNEY v' 1940- -'r. R. HARRISON CONTROL SYSTEM Original Filed Jan"9, 1937 2 Sheets-Sheet 2 M FR BF BF 1 s 00 0 0 "GF F GR e INVENTORTHOMAS R. HARRIS m ON ATTORNEY i Patented Now. 26, 1940 CONTROL SYSTEMThomas R. Harrison, Wyncote, Pa., assignor to The Brown InstrumentCompany, lhiladelphia, Pa, a corporation of Pennsylvania Originalapplication January 9,

Divided and this application May 24,

1937, Serial No.

. 1939', Serial No. 215,505

' 4 Claims.

The general-object of the present invention is to provide an improvedapparatus for producing control effects in accordance with thevariations in a variable condition, such as a variable tom perature,rate of flow or pressure. The present invention may be employed withadvantage in producing control efiects for such purposes as the power,or relay,adjustment of the indicating pointer or recording pen of ameasuring instrument in accordance with the deflection of a sensitivemeasuring unit, the control of a fuel valve or switch, the actuation ofdistant reading instruments, remote control operations, and

for

many other purposes in which a power actuated device or relay isoperated in accordance with changes in the value of a variablecondition.

, in accordance with the present invention, 1 create control effectswhich are of fixed predetermined magnitude and create opposing con troleffects, each equal to, less than, or greater than a corresponding oneof the first mentioned effects, accordingly as the variable condition isequal to, or differs in one direction or the other from a correspondingone of the first mentioned efiects. In my prior application, Ser,

119,761, filed Jan. 9, 1937, of which the present application is adivision, I have disclosed varl= ous forms of apparatus, including thoseilluw trated and described herein, for creating control effects of thecharacter just described, and for utilizing those efieots in controllingreversible electric motors of various types.

The general principles of the invention dioclosed in my said priorapplication are of especial advantage when utilized, as disclosed andclaimed herein, in controlling a reversible electric relay motor of aknown type which is adapted to operate in one direction, or the other,or to stall, cordingly as one or the other of two energiainu.

actions is impressed on the motor or both cner gizing actions aresimultaneously impressed thereon. The use of such a rnotor for controlpurposes avoids the motor ov'errunning or coast ing, experienced whenthe energization of a motor of more usual type is interrupted.

The use of such a motor controlled in the man-- ner disclosed herein, isespecially advantageous for example when used in a self-balancingtentiometer instrument to adjust the slide wire resistance and pencarriage of the instrument, in accordance with the deflection of thegalvanometer connected to the potentiometer circuit. In suchpotentiometric uses of the invention, the galvanometer actuating currentis ordinarily minute, and the galvanometer deflection impulsecorrespondingly small, and the galvanometer actuating current or aminute control= ling current regulated by the galvanometer, mayadvantageously ice amplified tor the purposes of the present inventionby the use of electronic 3111-."

pliiying means.

The various leatures of novelty which characterize my invention arepointed out with particu= larity the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specific olojects attained with its use,reference should be made the accompanying drawings and descriptivematter in which I have illustrated and described preferred emloodimentsoi the invention.

@i the drawings:

l is a diagrammatic representation of one embodiment of my invention;

shown part F l; and

Flo, is a diagram illustrating a modification oi a portion or the motorcircuit arrangement shown in l. I

In the form or the invention diagrammatically illustrated in Fig. l, agalvanometer G a pointer G is adapted to respond to unbalance in a nullpoint potentiometric circuit, the latter of which may he of any suitabletype, such as the Brown potentiometric circuit disclosed. my priorPatent 13993 12 issued February 21, 1933. Such circuits are well=known,and it is suidcient for the present purposes to note that the circuitshovm comprises a circuit branch including a source oi variablepotential to be measured, such for example, as the thermocouple Th, anopposing circuit branch including a source of known potential such asthe cell i, and resistors R, a variable portion or the last of which mayhe connected into the op osed branches by means of a sliding contact Rwhereby the respective sheets or" the variable and known sources aremade equal and opposite, and the galvanometer ls thus brought into itsneutral undeflecteo position, when circuit is balanced for a given valueof the M. F. oi the thermocouple Th with contact R in a correspondingposition. The position or" contact alone the resistors R is then measureof the value of the thermocouple M. R, and may then serve as a measureof th temperature to which it is exposed.

in. the form of my invention shown in Fig. l, the contact R is adjustedback and forth along resistors R in response to galvanometer deflection,by means comprising a reversible electrical Fig. 2 is a diagrammaticelevation of apparatus ill motor M connected to contact R for rotationof the latter, when the motor is rotated, and galvanometer contactingmeans for selectively energizing the motor I! in one direction or theother and for a period depending upon the direction and extent ofgalvanometer defiection.- The motor M is of the split phase shading poleinduction. variety, having a main field winding MI energized directlyfrom alternating current supply conductors 1.. and I? and shading fieldThe galvanometer contacting, or controlled, means includes a pair ofarms GP and GR. which are given oscillatory motion in regular cyclesfrom an initial position into a final podtion during which movement. thearm GR is adapted to e gl ethepointerGandthearmGFisadapted to engage afixedstud l". The travel of arm (31'' is thus fixed, the arm Gl'movingineachcycle fromafixedinitialpositiontothepositionin which it contactsstud 1", but the travel of arm- GR. is variable, the arm GR moving ineach cycle from a fixed initial position corresponding to the initialposition of arm G1". to a position in which it contacts the galvanometerpointer G. Arms Gl'andGRareurgedhymeansofsprlngGP' and GR in a directionto make contact respectively with members 1" and G, and are permittedtodoso,orarepreventedfromdoingsobyan oscillating actuating pin E, whichonce in each cyciecarriesbotharmsGFandGRinthecounterclockwise directionto an initial position, and

permitsthearmsthereaftertoturnclockwisetoward engagement with members1'' and G.

The pointer G, which is made of electrically conducting material, isperiodically clamped by means of a clamp C against an abutment C. Thestud F and clamp C areelectrically connected together and are connectedby a conductor FL into a motor energizing and control circuit to whichthe arms GF and GR are connected by conductors 2 and I, respectively,and to which the shading field windings M1", MP MR. and MR of the motorM are also connected. The motor energizing thearmGRwiththepointerGZwiththearm.

GP out of contact with'the stud I", energizes the shading field windingsfor rotation of the motor M in the reverse direction. and that thesimultaneous engagement of the arms GF and GR with the stud F andpointer G, respectively. energizes theshadingfieldwindingstostallthemotorM.

In order to selectively energize motor 1! for rotation in one directionor the other dependent upon the direction of deflection of pointer Gfrom its mid or null position and to make the extent of rotation of themotor proportional to the extent of deflection of the galva'nometer, thefixed studFisarrangedtobecontactedbyarmGI'atthemidpointintheoscillatorytravelofarmsClrI' and GR, at which point thegalvanometer pointer i G will also be contacted, while clamped, by armGRJfatthattimethegalvanometerisinitsnull ably as hereinafter described,independmt inter- 'ruptor means are provided for deenergising the motor.

If the galvanometer when clamped is defiectedtotherightasseeninl'lghthecoumterclockwise movement of arms G1" and GRwill result-in engagement of arm 0? with stud 1" before arm GR. contactspointer G. Such independent engagementofarmG-I' withstudlwillresultinenergization of the shading field windings M1",

M1 MR. and MB. for rotation of the motor Min one direction. The rotatimof motor I will continue until the arm GR contacts pointer G, therebyenergizing the shading field windings to stall the motor. If thegalvanometer. when clamped, is deflected to the left, thecounterclockwiserotationofarmsGFandGRwillfirstbring the arm GR intocontact with the pointer 0' thereby energizing the shading fieldwindings for a rotation of the motor I in the reverse direction, whichwill be terminated by engagement of arm GP with the stud F, whereby theshading field windings are so energized as to stall the motor. As willbe understood, the rotation of motor 1! will move contact R in adirection to restore the galvanometer pointer G to its null position.

It will be noted that in view of the cyclic character of the operation.the period of energisation of motor M in one direction or the other maybe, andasshowniamadeproporticnaltotheextent of deflection of pointer 0'.The device, is thus far described, may be utilized to provide twoenergising periodsfor motor M, each onal to the extent of deflection.Thus the element 3' in turning counterclockwise during a left-handdeflection of pointer G will pick up arm GP and may thereby efiectivelyenergize the motor shading field windings to rotate the motor in onedirection until element E mums: picks up arm GR and thereby efiectivelythe field windings. Similarly on a right-hand defiection element 13: mayfirst pick up arm GR. and thereby energize the shading field windingsfor rotation of the motor in the reverse direction until arm Gl" ispicked up by element 3' and the shading fields are efiectivelydeenergized.

In practice. however, it is desirable that the motor fields MP, M1", M3and MR should be deenergized throughout the periods in which either armGP or GR. is being returned to its initial position by the element E. Tothis end I provide an interrupi'or switch 8 whereby the circuit formotor M is opened at the end of the first half of the cycle beforeeither arm G1" or GR. is picked up by element 8'. and remains openduring substantially the entire counterclockwise movement of element 8'.

Fig. 2 diagrammatically illustrates the form of mechanism for producingthe oscillatory. movements of the arms 61'' and GR. in suitably timedrelation with the clamping of thegalvanometer pointer G against theabuhnent C.- Said mechanism comprises a cam Diournalled atDP andcontinuously rotated through gearing D by'a shaft D' which is driven bya motor. not shown. "I'hecamDisprovidedwithanedgeconfigured to provideedge seginents'llD and D. and is rotated counterclockwise. A roller CDcarried by a lever .CD which is pivoted on CD9, and has a gravitationalbias for coimterclockwise movement. .whereby the roller CD is held inengagement with the edge of thecam D.

Assh0wninFlg.2,therdlerCD'isinengagement with the cam edgeportion-Ifi,and the lever Cl? is at the limit of its movement in thecounterclockwise direction, and its arm CD extends through a slot (3 inthe pivoted clamping member C, and holds the clamping edge of saidmember in an elevated position in which it engages the galvanometerpointer G' and clamps the latter against the stationary abutment Thelever CD carries a switch bracket CD8 for the mercury switch S, and whenthe lever CD is moved in the position shown in Fig. 2, the switch S istilted into its closed circuit position. As the continuous rotation ofthe cam D in the counterclockwise direction terminates the engagement ofthe roller CD with the cam edge portion D and effects engagement 0! theroller CD first with the cam edge portion D and then with the cam edgeportion D the clamp C is permitted to move down under the action ofgravity thus releasing the galvanometer pointer G, and the switch S isturned toits open position.

The operating means for the element E whereby the oscillation of arms GRand GE is con trolled, includes a roller D, carried by cam D, and

displaced from the axis of rotation of the latter,

' which engages the edge of a lever DE. The latter is loosely pivoted atGDP, and carries a pin DE adapted to engage the cam surface E of a leverE. Lever E is loosely pivoted at GEP, which is also the pivot for leversGF and GR, and carries the previously mentioned element E. The lever Eis given a counterclockwise bias by counterweight E, which is suflicientto overcome the force of springs GR and GF', so that edge E? exerts aforce on pin DE tending to turn lever DE into engagement with roller D.Movement of lever E counterclockwise is limited by its engagement withstationary stud P As the roller U turns into the position shown in Fig.2, it turns the lever DE counterclockwise, and thereby turns the lever Eclockwise and thus permits arms GR and GP to move clockwise intoengagement with the pointer G and pin F, respectively.

In Fig. 2, the arms GR and GF are shown the limits of'their movements inthe clockwise direction, and it will be noted that the roller D is thenin its dead center or tangential position with respect to the edge oflever DE, and the roller is about to leave edge segment D and willshortly thereafter be engaged by edge D before pin it has permitted anyappreciable movement of arms GR and GF to the left. 'The'switch S ismoved to open position, as the arms GR and GF counterclockwise arerestored to their initial positions, and thus opens the motor energizingcir cult, preventing operation of the latter durin the movement of thearms GR and GP to the left, and also obviates any circuit opening actionat the galvanometer pointer or at the stud r, which might result inobjectionable arcing. Gonceiw ably, the dwell D might be dispensed withbut when provided, it insures positive tilting of switch S to its ofiposition before the arms GR and GF leave the pointer G and stud F,respectively, and insures further that the arms GR. and GF are returnedto their furthermost position in the counterclockwise direction beforethe clamp C releases the pointer G.

The galvanometer zero is set at the mid of the, abutment C'which may begraduated with divisional. markings to indicate the galvanometerposition, the edge of stud F which is contacted by arm GF is disposeddirectly under the edge of the pointer contacted by arm GR wherebysimultaneous engagement of the arms with their respective contactingelement .may be effected when the galvanometer is in zero position. The

' anced as the result of movements given the contact R along theresistors R by the motor M. As the galvanometer pointer is deflected inone direction or the other, and the arms GR and GF make engagement withtheir respective contacting elements, the motor M is energizedfor'rotation in one direction or the other for a period depending uponthe direction and extent of galvanometer deflection, and moves thecontact R to a new position along the slide wire resistances R toproduce an effect in the potentiometric circuit equal and oppositetothat which gave rise to the galvanometer deflection.

The energizing circuit for the motor M shown in Fig. 1, includes a twinamplifier tube B such as a tube of the 53, heated cathode type,combining in one envelope two triodes, comprising anodes or plates BFand ER, grids Bi and Br, and filament means for heating a common cathodeBC. Necessary direct current voltages are obtained from a standardrectifier arrangement including a rectifier tube W, a power supply transformer T and a filter condenser CO. The rec tifier W may be any suitablefull wave rectifier, such as an 80 is direct current power supplydevices which operate from an alternating current supply line. Thetransformer as shown, includes a primary winding T connected to thealternating current supply conductors L and L and wound on a common corewith secondary windings T T T T and The windings T and T are filamentheater windings and through conductors W and TB supply filament currentto the tubes W and Id, respectively. Connection is made by a conductor ii to the cathode BC oi tube B, irorn a center tap T on the winding Theterminals of the winding 1" are connected to the plates oi the rectifiertube W and the electronic circuit is completed through the triodes oftube 13, and conductor ,t, which the motor shading field tdndings "ouME, ME and m are inserted, to the filament Z of rectifier tube W, and

through the rectifier tube W back to the wind- 3 tube, adapted for usein iii) The characteristics of the tube B are such that with its gridsBy and 331- at zero potential with respect to the cathode BC, the :platecurrents through the tube will be reduced to a negligible value. when avoltage or signal is applied -to either grid Bf or Br, however, currentof substantial value will how in the corresponding plate circuit duringthe positive half or the gridvoltage cycle. During the negative half ofthe grid voltage cycle the current in theplatecircuitwillbereducedtosero. Binoethe tube B will be conductive onlyduring the posi- 5 tive half of the grid voltage cycle. the platecurrent flowing will. therefore, be pulsaflng having the frequency ofthe alternating current impressed on the grid.

As shown in Pig. 1. the windings MP, II", MR 10 and MRareconnectedinserieswiththephte to cathode resistances of the triodes oftube 3. and are energized for selectively producing motor rotation inone direction or the other by applying to these windings a pulsatingcurrent having 16 the same frequency as the alternating current suppliedby conductors L and L and in phase or 180 out of phase therewith. Themotor is stalled by applying both of said pulsating cur-' rentssimultaneously on said motor. I so 'Ihemalnfleldwindingmisenergizeddirectly from the line, but is of such highinductance that the current through this winding lags the line voltageby approximately 90. The tube 8, acting as a resistance, tends to keepthe current as in the shading ileld windings approximately inphasewiththelinevoltagesothatineflectthe motor M is operated as a splitphase motor for rotation in one direction or the other as thecurrent'through the shading field windings is selec- JOtivelycontrolled.Ifdesiredacondenserofsuitablecapacitymaybeconnectedacrossthetuminalsoftheauxiliarywindingsforholdingthecurrent through these windings more closely to the desired phase angle,and for transforming ggthepulsatingcurrentproducedbythetubenBfofthetubeBandthesecondterminalofthewinding'flisconnectedbyaconduotoritothe grid 131' of the'tuhe B.Furthermore. the con- I nections are such that when the arm 81'' engagesthe stud l". the varylns-potential bias impressed on the grid BI is 180out of phase with the potential bias impressed on the grid Br when thearm GR engages the galvanometer pointer G.

WhenthearmGFengagesstudFbeforethe arm GR engages the galvanometerpointer G. the potential bias impressed on the grid B} will create apulsating current flow through the shading fleld motor w indinls MP.M1", MR and IR .whichwillbedisplacedinphasefromtlmecur-v rent flow inthe winding m by approximately 90andasaresultarotatingmagnetlciieldwillbeestablishedinthemotortoproduoerotation ofthe motorrotorinapredetermined direc- .I tion. When the arm GR engages thegalvanom-- eter pointer G before the arm GP ensues thestudlfithepotentialbiasimpremedonthegrld Brwiil create apulsatingcurrent flowthrowh the shading field-windings which will be dis- "placedapproximatelyOO'i'romthecurrentflow inthe winding MI. but the directionof thephase displacementoi'thecurrentsinthetwowindings will be oppositeto that in theflrst mentkmed case. With either direction of the phasedisflplacementofthecurrentflowintheshading roximately 90' from thecurrent The two current ilows g 9 Eg direction.isinengagementwiththestudl'andthearm 'Gnismoving clockwise toward,buthasnot yet-u engaged the galvanometer pointer G, a signal displacedapproximately 90 in the opposite dilorectionfromthecurrentilowinthemainfleld tivelyimpressingcontrolsignalson thebiasing gridsofthetwimordouhletriodetubehmay".beuaedwithadvantageinaninductionmotor energizing circuit arrangementdiflerent from thatshowninl'lg. Lonesuchdiiferentarrangementb'eingshownbywayofexampleinFigJ.

Theinductionmotorll'showndiagrammatisupply conductors L and L, whichsupplies alternating current voltage to the primary winding T of thetransformer '1.

As a result of the action of the condenser MC, the current flowing inthe winding MI of Fig. 3, will lead the line voltage by approximately90. When :the arm GF engages stud F before the arm GR engages thegalvanometer pointer, the potential bias impressed on the grid B willcreate a pulsating current fiow through the motor winding MFR, whichwill be displaced in phase from the current flow in the winding M1" byapproximately 90 and as a result a rotating magnetic field will beestablished in the motor to produce rotation of the motor rotor in apre-. determined direction. When the arm GR. engages the galvanometerpointer G before the arm GF engages the stud F, the potential biasimpressed on the grid Br will create a pulsating current flow throughthe motor winding MFR, which will be displaced approximately 90 in phasefrom the current flow in the winding MI, but the'direction of the phasedisplacement of the currents in the two windings will be opposite tothat in the first mentioned case. As in the Fig. l arrangement, witheither direction oi the phase displacementof the current fiow in thewinding MFR relative to that in the winding M1, the two current fiowswill subject the rotor of the motor to a magnetic field rotating in adirection selectively dependent upon the direction of said displacementand produce a rotor rotation in the same direction in which the magneticfield rotates.

Notwithstanding the specific diflerences between the arrangements ofFigs. 1 and 3, the two arrangements are alike in their more importantnovl characteristics. In each case. the main and auxiliary fieldwindings of the induction motor are so combined with a pair of electronemission devices, that the rotor of the motor will be subjected to theaction of a magnetic fieldv rotating in one direction, or the other,accordingly as a signal or potential'bias is impressed on the grid ofone or the other of the two electronic devices. In each case, also, the

simultaneous impression of signals or bias po- 1 tentials of similarstrengths on the grids of the I two devices will prevent the magneticfield then formed from rotating.

As will be apparent to those skilled in the art, the arrangementsillustrated and described for producing control effects varying indirection and magnitude with the position of a galvanometer pointerdeflecting in accordance with variations in a variable condition,possess important practical advantages for control instrument use, be-'cause 01 their reliability and definite action, and because theycontribute to instrument simplification, and particularly because of thesimplicity, reliability and other desirable operating characteristics ofmotors or the rotating field type.

While in accordance with the provisions of the statutes 1 haveillustrated and described preferred embodiments of the presentinvention, those skilled in the art will understand that changes may bemade in the form of the apparatus disclosed without departing irom thespirit of my invention as set .iorth in the appended claims,

and that some ieatum oi the present invention may sometimes be used withadvantage, without a corresponding use of other features.

Having now described my invention, what ll claim as new and desire tosecure by Letters Patent, is:

l. A control circuit for a reversible electrical rotating field motorhaving two windings inductively disposed with respect to a rotor, comprising a pair of electronic valves, each oi said electronic valvesincluding an anode, a cathode and a grid, means connecting the anode tooath Iii) ode impedances of said valves in parallel, a source I ofvoltage connectedto said valves and to one of said field windings, avoltage source of varying magnitude connected to the other of saidwindlugs, and means for selectively applying on one grid a secondvoltage of varying magnitude displaced in phase relation from the firstmentioned varying voltage and for selectively applying the firstmentioned varying voltage on the other grid of said electronic valves.

2. A control circuit for a reversible electrical condenser motor havingtwo field windings inductively disposed with respect to a rotor, com

' prising a pair of electronic emission devices, each of said electronicemission devices including an anode, a. cathode and a grid, meansconnecting the anode to cathode impedances of said emission devices inparallel, a source of voltage connected to said emission devices and toone of said field windings, a voltage source of varying magnitudeconnected to the other of said windings, and means for selectivelyapplying on one grid a second voltage of varying magnitude displaced inphase relation from the first mentioned varying voltage and forselectively applying the first men tioned varying voltage on the othergrid of said electronic emission devices.

3. A control circuit for a reversible electrical shading pole motorhaving a main field winding and a plurality, of shading field windings,comprising a pair of electronic emission devices, each of said electronemission devices including an anode, a cathode and a grid, meansconnecting the anode to cathode impedances of said emission 7 xtivelydisposed with respect to a rotor, comprising a pair of electronicemission devices, each of said electronic emission devices including ananode, a cathode and a grid, a source of direct current voltage, aseries connection between said source of voltage and one of said fieldwindings including the anode to cathode impedances of said emissiondevices in parallel, a voltage source of varying magnitude connected tothe other of said windings, and means for selectively applying on onegrid a second voltage of varying magnitude displaced in phase relationfrom the first mentioned varying voltage and for selectively applyingthe first mentioned varying voltage on the other grid of said electronicemission devices.

THOMAS R. HARRISON.

